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In this article, we propose an approach to reconstruct the timing of human activity at Points Cave, an Upper Paleolithic rock art site located in the middle of the Ardèche River Gorge (Rhône valley, France), based on the dating and characterisation of a stalagmite containing soot. Points Cave ('Grotte aux Points' in French), also called the 'little sister of Chauvet Cave', is famous for its parietal art including a series of dots made of palm prints. A large number of stalagmites formed in the cave during the last 500 ka. However, quarrying of the cave floors during historic times led to the partial destruction of the sedimentary deposits, and many of the stalagmites were found lying on the floor. In particular, one of them (STM‐18‐04) showed the presence of at least four dark layers in cross‐section, which appeared as possible remnants of fire‐related activities in the cave. Despite being present at the same site, no other specific link between STM‐18‐04 and the rock art has been documented. This stalagmite, however, allows us to identify phases of human presence, located at the cave entrance. To do so, we performed a series of analyses to determine its period of growth and the nature of the dark layers that it contains. Scanning electron microscopy and Raman microspectroscopy confirmed that the dark layers include soot, and uranium‐series dating indicated that the fire events occurred, respectively, around 14,200–14,100 and 12,500 years ago, in agreement with the radiocarbon ages of charcoal specimens recovered from the excavation areas nearby. We thus highlighted phases of human activity at the site during the Upper Magdalenian and/or beginning of the Epipaleolithic. By comparing our results with the regional paleoclimatic record, the soot layers trapped in the stalagmite appear to be synchronous with two cold periods, likely the Older Dryas and the Younger Dryas. [ABSTRACT FROM AUTHOR]

Meaningful analysis of uranium‐series isotopic disequilibria in basaltic lavas relies on the use of complex forward numerical models like dynamic melting (McKenzie, 1985, https://doi.org/10.1016/0012-821x(85)90001-9) and equilibrium porous flow (Spiegelman & Elliott, 1993, https://doi.org/10.1016/0012-821x(93)90155-3). Historically, such models have either been solved analytically for simplified scenarios, such as constant melting rate or constant solid/melt trace element partitioning throughout the melting process, or have relied on incremental or numerical calculators with limited power to solve problems and/or restricted availability. The most public numerical solution to reactive porous flow, UserCalc (Spiegelman, 2000, https://doi.org/10.1029/1999gc000030) was maintained on a private institutional server for nearly two decades, but that approach has been unsustainable in light of modern security concerns. Here, we present a more long‐lasting solution to the problems of availability, model sophistication and flexibility, and long‐term access in the form of a cloud‐hosted, publicly available Jupyter notebook. Similar to UserCalc, the new notebook calculates U‐series disequilibria during time‐dependent, equilibrium partial melting in a one‐dimensional porous flow regime where mass is conserved. In addition, we also provide a new disequilibrium transport model which has the same melt transport model as UserCalc, but approximates rate‐limited diffusive exchange of nuclides between solid and melt using linear kinetics. The degree of disequilibrium during transport is controlled by a Damköhler number, allowing the full spectrum of equilibration models from complete fractional melting (Da=0) to equilibrium transport (Da=∞). Access the full executable Jupyter notebook version of this manuscript here. Key Points: Cloud‐based Jupyter notebook presents an open source, reproducible tool for modeling U‐series in basaltsEquilibrium and pure disequilibrium porous flow U‐series models with 1D conservation of massScaled porous flow model introduces incomplete equilibrium scenario with reaction rate limitations [ABSTRACT FROM AUTHOR]

The Tierra Blanca (TB) eruptive suite comprises the last four major eruptions of Ilopango caldera in El Salvador (≤45 ka), including the youngest Tierra Blanca Joven eruption (TBJ; ∼106 km3): the most voluminous event during the Holocene in Central America. Despite the protracted and productive history of explosive silicic eruptions at Ilopango caldera, many aspects regarding the longevity and the prevailing physicochemical conditions of the underlying magmatic system remain unknown. Zircon 238U‐230Th geochronology of the TB suite (TBJ, TB2, TB3, and TB4) reveals a continuous and overlapping crystallization history among individual eruptions, suggesting persistent melt presence in thermally and compositionally distinct magma reservoirs over the last ca. 80 kyr. The longevity of zircon is in contrast to previously determined crystallization timescales of <10 kyr for major mineral phases in TBJ. This dichotomy is explained by a process of rhyolitic melt segregation from a crystal‐rich refractory residue that incorporates zircon, whereas a new generation of major mineral phases crystallized shortly before eruption. Ti‐in‐zircon temperatures and amphibole geothermobarometry suggest that rhyolitic melt was extracted from different storage zones of the magma reservoir as indicated by distinct but synchronous thermochemical zircon histories among the TB suite eruptions. Zircon from TBJ and TB2 suggests magma differentiation within deeper and hotter parts of the reservoir, whereas zircon from TB3 and TB4 instead hints at crystallization in comparatively shallower and cooler domains. The assembly of the voluminous TBJ magma reservoir was also likely enhanced by cannibalization of hydrothermally altered components as suggested by low‐δ18O values in zircon (+4.5 ± 0.3‰). Plain Language Summary: The collapse of a volcano edifice into its shallow magma chamber can produce one of the most dangerous single events in nature, known as a caldera‐forming eruption. The TBJ eruption in El Salvador is of this kind and occurred around 1,500 years ago, having a profound impact on Maya societies. Because of this, it is crucial to understand the inner workings of caldera‐forming eruptions to assess volcanic risks and their mitigation. Beneath Ilopango caldera, the micrometer‐sized radioisotopically datable mineral zircon grew within different storage levels of a silica‐rich magma reservoir suggesting continuous melt presence for up to ca. 80,000 years prior to eruption. The time information given by zircon contrasts with that extracted from other, more abundant minerals from the same rocks (<10,000 years). We explain this time difference between coexisting minerals by the ability of melt to carry along small zircon crystals, whereas coeval, larger, and more abundant minerals are left behind in the partially solidified portion of the magma reservoir. Once the segregated melt coalesced in a shallower and dominantly liquid magma chamber, major minerals resumed crystallization shortly before eruption. In addition, this new magma incorporated parts of older magmatic rocks from preceding volcanic cycles, thus generating even larger magma volumes. Key Points: U‐Th zircon ages for the last four explosive eruptions of Ilopango caldera reveal a long‐lived magma reservoir (>80 kyr)Contrasting residence times for major minerals and zircon suggest extraction of zircon along with evolved melt from crystal residueMelt extraction from vertically extensive, thermally zoned magma reservoir [ABSTRACT FROM AUTHOR]

Travertine deposits preserve an invaluable record of both ancient and modern fluid flow. The goal of this study is to reconstruct spatial and temporal patterns in travertine deposition associated with tectonic and climatic controls along the Lucero Uplift in New Mexico, USA. Uranium‐series ages of travertine deposits in the Lucero Uplift range from 0.94 ± 0.01 to 592 ± 110 ka, indicating that travertine formation has been episodically active since at least ∼600 ka. We find minimal evidence to attribute glacial and interglacial cycles to travertine formation in the Lucero Uplift. δ13C values in travertine deposits range from 2‰ to 9‰ (Vienna Pee Dee Belemnite), δ18O values range from 21‰ to 25‰ (Vienna Standard Mean Ocean Water). Positive correlation between travertine δ13C and δ18O values indicate travertine formation is closely associated with various degrees of CO2 degassing. 87Sr/86Sr values in travertine deposits range from 0.714 to 0.717 and (234U/238U)i values exhibit a remarkably wide range from 3.6 to 9.3, indicative of fluid‐rock interaction during deep crustal circulation in more radiogenic basement rocks. Reconstructed δ13C, δ18O, and (234U/238U)i values in the inferred deep fluid sources showed systematic variations with travertine formation ages, while 87Sr/86Sr values remain relatively constant. Based on dating of undeformed travertine deposits, which overlie tilted Santa Fe Group units, and high (234U/238U)i we infer that the Santa Fe fault has not produced a ground‐rupturing earthquake within the last 490 ± 52 to 592 ± 110 ka (2σ). Our study suggest that travertine formation is driven by fluid flow facilitated by tectonic and mantle structures. Key Points: Travertine deposits of the Lucero Uplift have been forming episodically since at least ∼600 ka through both glacial and interglacial periodsCarbon, oxygen, strontium, and uranium isotope data indicate mixing of deep and shallow crustal fluid sources involved in travertine formationTravertine formation is mainly driven by fluid flow influenced by regional tectonic (Rio Grande rift) and mantle (Jemez Upwelling) structures [ABSTRACT FROM AUTHOR]

To investigate whether the source of the globally occurring garnet signature in mid‐ocean ridge basalt (MORB) is "true" (imparted by melting a garnet‐bearing source) or "apparent" (produced without the involvement of garnet), we present the basalt petrogenesis model Petrogen. Petrogen is built on Kinzler and Grove (1992a, https://doi.org/10.1029/91JB02841) and Behn and Grove (2015, https://doi.org/10.1002/2015JB011885) and calculates the major element, trace element, and isotopic compositions of primary lherzolite‐saturated mantle melts and their subsequent evolution to eruption. This model is experimentally calibrated for melting in the plagioclase, spinel, and garnet fields with and without small amounts of water. Petrogen predicts that garnet‐lherzolite melting requires small mantle porosity (ϕ = ∼0.1%) and enriched (NaK# > 0.1), hot (>1400–1450°C), and damp mantle (>350–700 ppm water) sources. When garnet‐lherzolite melting does occur, the fraction of melting that takes place in the garnet field is not sufficient to impart a recognizable true garnet signature in the major and trace element composition of pooled melts except at ultraslow‐spreading rates (half rate ≤ 0.5 cm/yr). Therefore, for ambiguous garnet trace element signatures in MORB to be "true" would require that they are near‐fractional garnet‐lherzolite melts or garnet‐pyroxenite melts diluted by mixing in random proportions. While we do not test the process of random mixing, we find that near‐fractional and pooled melts of variable major and trace element mantle peridotite compositions at different mantle potential temperatures can explain the range of garnet signatures in MORB. For spinel‐peridotite melting to support garnet signatures requires mantle porosities ϕ = ∼0.1%; however, plagioclase‐peridotite melting, under specific circumstances, can explain MORB garnet signatures with ϕ = ∼1%. Key Points: The major element composition of garnet peridotite melts provides critical evidence for identifying garnet signatures in MORBsGarnet signatures in MORBs are diverse and reflect melting of compositionally and thermally variable mantle without garnetShallow melting of plagioclase peridotite can explain MORB major and trace elements and U‐series isotopes with mantle porosity ϕ ≥ 1% [ABSTRACT FROM AUTHOR]

Kiacatoo Man, a large, rugged Aboriginal adult buried in the Lachlan riverine plains of southeastern Australia, was discovered in 2011. Laser‐ablation uranium series analysis on bone yielded a minimum age for the burial of 27.4 ± 0.4 ka (2σ). Single‐grain, optically stimulated luminescence ages on quartz sediment in which the grave had been dug gave a weighted mean age of 26.4 ± 1.5 ka (1σ). Luminescence samples from the grave infill and from sediment beneath the grave exhibit overdispersed dose distributions consistent with bioturbation or other disturbance, which has obscured the burial signal. The overlap between the minimum (U‐series) and maximum (luminescence) ages places the burial between 27.0 and 29.4 ka (2σ). Luminescence ages obtained from the channel belt of between 28 ± 2 and 25 ± 3 ka indicate that fluvial sedimentation was occurring before the Last Glacial Maximum, which is consistent with the broader geomorphic setting. Together, these results are internally and regionally consistent, and indicate that Kiacatoo Man was one of the more ancient individuals so far identified in Australia. His remains are important to our understanding of patterns of biological variation and other processes that have shaped people in the Murray‐Darling Basin through time. Copyright © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that bifacial technology (Acheulian, Mode 2) arrived in Europe during the early Middle Pleistocene, i.e. significantly earlier than previously proposed. In northern France and Britain, much of the age attribution for these assemblages has been based on biostratigraphy and lithostratigraphy rather than absolute dates. This study presents a systematic application of electron spin resonance (ESR) dating of sedimentary quartz and ESR/U-series dating of fossil tooth enamel to key Acheulian sites of this area. Although the age estimates have large associated uncertainties, most of the derived dates are consistent with existing age estimates. The new chronologies and the problems associated with dating material of early Middle Pleistocene age are discussed. In Britain, the earliest archaeology (cores and flakes, Mode 1) is older than Marine Isotope Stage (MIS) 15, whereas localities containing Acheulian technologies span late MIS 15/MIS 13 through to MIS 9. A similar pattern is seen in northern France although age estimates from sites such as la Noira suggest the possible appearance of the Acheulian in central France as early as MIS 17. The dates presented here support the suggestion that the earliest Acheulian appeared in NW Europe during the early Middle Pleistocene, significantly after its appearance in the southern parts of the continent. [ABSTRACT FROM AUTHOR]

The accuracy of 231Pa-235U measurements can be readily assessed using a secular equilibrium reference material (RM), but a secular equilibrium RM is also required to calibrate the 233Pa spike used in 231Pa determinations. The only silicate RM commonly accepted to be in secular equilibrium is Table Mountain Latite (TML) and so an additional reference is required. Our measurements on the widely available USGS BCR-2 (Basalt Columbia River) rock powder yielded (231Pa/235U) = 0.997 ± 0.013 2s (n = 10), indicating its value as a secondary reference to test the fidelity of U-Pa determinations. Such a reference material additionally provides a useful check on data reduction, which our literature survey highlights can lead to discrepancies of up to 53% between reported (231Pa/235U) activity ratios and corresponding U and Pa concentration data. [ABSTRACT FROM AUTHOR]

The methods that can be used for the direct dating of human remains comprise of radiocarbon, U-series, electron spin resonance (ESR), and amino acid racemization (AAR). This review gives an introduction to these methods in the context of dating human bones and teeth. Recent advances in ultrafiltration techniques have expanded the dating range of radiocarbon. It now seems feasible to reliably date bones up to 55,000 years. New developments in laser ablation mass spectrometry permit the in situ analysis of U-series isotopes, thus providing a rapid and virtually non-destructive dating method back to about 300,000 years. This is of particular importance when used in conjunction with non-destructive ESR analysis. New approaches in AAR analysis may lead to a renaissance of this method. The potential and present limitations of these direct dating techniques are discussed for sites relevant to the reconstruction of modern human evolution, including Florisbad, Border Cave, Tabun, Skhul, Qafzeh, Vindija, Banyoles, and Lake Mungo. Yrbk Phys Anthropol 49:2-48, 2006. [ABSTRACT FROM AUTHOR]